Push buttons are used on a variety of interfaces for controlling many different functions. Typically, each button is labeled with text, a symbol or some other visual indicator to indicate the specific function or state of activation. In this specification, any such text, symbol or visual indicator is referred to as a “graphic”. The graphic may then be controllably displayed when the button is pressed by a user, for example with back lighting being switched on or off to indicate, respectively, the activation or deactivation of some function.
In applications in which it is required or desirable to have a large number of different controls, a problem can arise if the number of buttons needed exceeds the space available while still having buttons large enough for ease of use.
A solution to this problem is to provide two different graphics on each button, with each graphic being associated with a different function. In this way, when the button is configured to perform a first function, a first graphic is displayed, and when the button is configured to perform a second function, a second graphic is displayed. However, another problem then arises regarding how to selectively display to the user only one of the two graphics at a given time, while concealing the unused graphic.
Some known solutions to this problem use color filters associated with each of the graphics in combination with two or more separate light sources providing two colors of illumination. By changing the illumination color, the graphic that is displayed to the user may be changed. However, with this method, there is a limit to the colors that can be chosen as they must be sufficiently different in wavelength for the filters to work to exclude one of the two graphics.
To enable each of the graphics to be more clearly distinguished, many prior art displays provide the graphics adjacent to each other, so that the presence of a first of the graphics does not alter the appearance of a second graphic even when only one of the graphics is illuminated. However, providing the graphics in this arrangement inevitably requires a button with a larger surface area than if the graphics overlapped.
It is an object of the present invention is to provide an improved means of displaying more than one graphic on a single display area, which may be a fixed display area or part of a movable control such as a button.